(695f) Thermochemical Methylation of Lignin to Produce High Value Aromatic Compounds

Patrick A. Johnston^a and Robert C. Brown^a,b

^aBioeconomy Institute, Iowa State University, Ames, IA 50011

^bDepartment of Mechanical Engineering, Iowa State University, Ames, IA 50011

Technical lignin, the byproduct from cellulosic ethanol production, is a potential feedstock for producing coumaric and ferulic acids. These biorenewable aromatic hydroxycinnamic acids can be upgraded to high value chemicals for the manufacturing of cosmetics, flavoring agents, and sunscreens. We hypothesize that during the fast pyrolysis of lignin aromatic acid esters can be recovered from coumaric, ferulic and other hydroxycinnamic acids using a methylation agent. In this study, technical lignin from cellulosic ethanol production was pyrolyzed in a micropyrolyzer with a methylation agent to produce gas chromatography (GC) detectable aromatic acid esters. Corn stover lignin from the enzymatic hydrolysis process and the organosolv process was combined with different methylation agents to produce, identify and quantify the hydroxycinnamic acid esters. High performance liquid chromatography (HPLC) with a diode array detector (DAD) was used to separate and quantify the extracted hydroxycinnamic acids from lignin for determination of yield recoveries.

To determine the actual total theoretical yield of coumaric and ferulic acid in the lignin an alkaline extraction method was used. The theoretical yields of coumaric and ferulic in the enzymatic hydrolysis lignin was 5.6% and 1.9%, respectively. The theoretical yields of coumaric and ferulic in the organosolv lignin was 7.7% and 2.9%, respectively.

The recoveries of the hydroxycinnamic acids from enzymatic acid hydrolysis lignin with different loading of methylation agent were compared using a micropyrolyzer at 500°C. Using tetramethylammonium hydroxide (TMAH) at 1µL produced recoveries of 40% coumaric and 37% ferulic compared to the theoretical extracted amount from the lignin. The recoveries at 5µL produced coumaric and ferulic acids concentrations of 68% and 55%, respectively. The recoveries at 10µL produced coumaric and ferulic acids concentrations of 84% and 69%, respectively.

The recoveries of the hydroxycinnamic acids from organosolv lignin with different loading of methylation agent were compared using a micropyrolyzer at 500°C. Using tetramethylammonium hydroxide (TMAH) at 1µL produced recoveries of 35% coumaric and 27% ferulic compared to the theoretical extracted amount from the lignin. The recoveries at 5µL produced coumaric and ferulic acids concentrations of 69% and 52%, respectively. The recoveries at 10µL produced coumaric and ferulic acids concentrations of 89% and 64%, respectively.